The present invention relates in general to spectrographic data collection, and in particular, to the utilization of a fiber bundle for the spatially resolved coupling of light to a spectrograph.
An assortment of analytical identification methods exist for the non-destructive testing of materials. Particularly, various spectroscopic methods, including Raman spectroscopy, can be advantageously employed in the practical identification of materials under test. By way of illustration, in dispersive Raman spectroscopy, a laser is used as an excitation source to focus light onto a particle. The laser light from the excitation source interacts with the Raman active chemical bonds of the particle impinged upon by the laser light to produce Raman lines that are shifted from the wavelength of the excitation laser by corresponding vibration frequencies. Light from the sample area of the particle is collected and is sent through a filter that blocks the excitation wavelength while passing the Raman-shifted wavelengths to a spectrometer. The spectrometer utilizes a grating that disperses light so that different wavelengths leave the grating at different angles.
The light from the grating travels to an optical detector, such as a charge coupled device (CCD) camera, where the divergence in angles causes light at different wavelengths to arrive on different pixels of the CCD to capture data representative of the Raman spectra of the particle under interrogation. The data captured by the CCD can be utilized as a signature, which is compared to a library of previously determined signatures to identify the material excited by the laser.